Heating unit for electric appliances



March 26, 1940. L H. COLLINS 7 2,195,848

HEATING UNIT FOR ELECTRIC APPLIANGES Filed larch 21,- 1938 Jill/622206 $62121 Collins M 9 Patented Mar. 26, 1940 Harry Collins, St. Louis, Ha, asaignor to Knappllmh pany, st. Louis, m, a

tlonofmaaonrl Application M :1. 1m. Serial No. 197,239

lOll-im.

My invention relates to electric appliances and particularly to heating units therefor. Among the objects of my invention is the provision of a new and improved composite heating unit comprised ofv a plurality of identical parts which can include any number of said parts to suit the requirements of the particular device in question.

Another object of my invention is the provision of a heating unit for an electric appliance comprising a plurality of individual parts each of which can be separately wound with a-heating element before assembly inthe device and then applied to the device in any suitable numbe:- with alternate parts reversed so that wires of the heating element will lie in a convenient position to be connected one with another.

A further object of my device is the provision of a composite heating unit made up of two or more identical parts consisting of a heat resistant material wound progressively from one end to the other with a heating element and provided additionally with anchoring apertures at one end so that when the parts are placed in any alternately reversed set of positions side by side, the ends of wires on adjacent parts will occupy a convenient position, one adjacent the other, so they may be connected by welding or otherwise and leaving two free ends of wire on the composite element thus formed, one of which can be threaded back through the sheets of insulating material in a position insulated from the coils of wire on each sheet to a point adjacent the wire at the other end so that connection canbe made to a power line at the-same point on an appliance.

With, these and other objects in view, my invention consists in the construction, arrangement and combination of the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claim, and illustrated in the accompanying drawing, in which:

Figure l is an end view of my device shown partly in cross section.

Figure 2 is a longitudinal elevation of my de-' vice insection taken on the line.2--2 of Figure 1 howing an even number of units.

" li'igureiisa view of the heating units alone showing an "odd number placed side by side.

{is a section on the line |-4 of Figure 2 to a larger scale; and v Figure a section on the line 55 of Figure 2 drawn't'd'a larger scale.

In the fabrication of heating units for electric appliances necessitating the use of resistance wire of the nature of nickel-chrome or other (Cl. 2l9-19) material wherein the wire must be ei'rposed without insulation or covering of any sort it has .been the practice .to assemble the heat resistant insulating sheets in a framework suitable for installation in an appliance flrst'and then towind the insulating sheets upon the resistant wire by hand so that the wire may form 6ne continuous coil from one point of connection through the entire appliance to another. Such a method of manufacture consumes considerable time and labor because of its required handwork which increases the expense and at the same time increases the chance of faulty construction due to inaccurate workmanship which cannot be avoided. Because of the usual intricate structure of the assembled heating units, it has not been possible by the machines now available to'wind the coil upon the unit by machine.

The present invention contemplates winding individual parts of the heating unit by machine and in addition so constructing these parts that although every part is identical with every other part, anchoring means is provided on each of the partssuch that they can be alternated and reversed in position in an appliance in order to have the ends of wire meet over the shortest pos-- sible span between the two adjacent parts and provide in addition an anchoring means for the loose terminals or ends of wire so that they may be guided in an insulated position through the unit to a single point of contact where they may be connected to a suitable power line.

In the embodiment of my invention here disclosed I have chosen an electric toaster A to illustrate the application of my novel composite heating unit B. The toaster is composed of a base l0 upon which is mounted a structure i2 for supporting the heating units and having doors l4 and I6 comprising the sides of the toaster for closing the appliance when in use. The structure I! is additionally provided with a somewhat V-shaped brace l8 to support the material to be a toasted and to prevent contact of the material with the heated portion of the appliance.

hole 36 while at the bottom there is a series of three holes 36, 46 and 62. It is to be borne in mind that each sheet is identical so that when reversed side for side, the holes just designated will occupy positions on alternate sides with respect to the general assembly of the sheet in the appliance.

Sheet 28 is wound with a coil of the resistance wire 34 beginning at the end H at which point the coil is connected by means of a wire 66 to one terminal 46 of the electric appliance. The wire is threaded through a hole 42 and wound in the form of a helical coil extending from the bottom of the .sheet upwards to the top where it passes through the hole 36. Sheet 36 is wound in exactly the same manner, but with a long end 50 of the resistant wire left dangling for a purpose subsequently to be described. This process of winding is done customarily by machine before the sheets are fastened in the frame.

Once wound and with the wire anchored in the holes provided for it in the sheets, the sheets are firmly attached to the'parts 26 and 22 of the frame, but it will be noted that the sheet II is reversed, side for side with the sheet 26. With this arrangement the holes 36 and 36' at the upper end of each will lie adjacent each other so that they are at the closest distance apart. The ends of wire protruding from the holes 36 and 36 are then cut of! short and welded or otherwise connected together. The span of wire between the holes will therefore be as short as possible. At the opposite end of the sheet III, the end of wire which would ordinarily pass through the hole 42 as does the wire in sheet 28, is pulled out of hole 42' and stretched across the sheet so as to enter hole 36 and is further-- more extended across the space between the sheets and threaded thence through corresponding hole 38 of sheet 26, hole 46 of sheet 28 and thence outward where the end 62 of the wire is connected by another wire 66 to a terminal 56 of the electric appliance.

Figure 5 shows the character of welded joint made between the ends of the wire protruding from the anchoring holes 36 and I6.

It will of course become apparent that any number of sheets similar to sheets 26 and 36 can be arranged side by side in order to build up a composite heating unit of any size desired as is illustrated in Figure 3. The sheets comprising such a unit are wound identically, as has been described in connection with Figure 2, but will of course be connected one with another alternately at the top and bottom of adjacent sets of sheets. A frame 60 at the top and a frame 62 at the bottom can be of such a suflicient length as will accommodate the desired number of sheets. In this modification also the sheets are wound exactly the same with coils of resistant wire and then attached in a frame with each alternate sheet reversed side for side. Connections between the ends of wire in each sheet are thus made as for example at the points 66 at the top and 66 at the bottom, it being of course necessary to withdraw the end of wire at the bottom from the corresponding hole-62', 62", etc. in order that the proper connection can be made.

areas As shown in Figure 3 an odd number of sheets have been used, and this necessitates bringing one free end 66 of the composite coil of wire out at the top of the unit, while the other free end of II comes out at the bottom. An insulated connection of the customary sort can readily be made from the end 66 downward to the bottoms of the sheets of insulating material and the wire then threaded through the'holes therein corresponding to the holes 36" and l6", l6 and II. etc., until it is brought to a point 12 adjacent the other end ll where each may be connected to terminals of an appliance in the same manner as has been described in connection with Figure 2.

Particular attention is. directed to the Joints 64 and 66 for example as illustrated in Figure 5. The joint is featured as a crimped Joint wherein the end of one wire or ribbon is folded around inside the folded end of the other. Both sides of the fold are then spot welded to produce a strong joint having a relatively low resistance.

There has thus been described a heating unit of extremely simple manufacture due to the fact that each part of a composite unit can be constructed exactly alike with the resistance wire wound on sheets of insulated material which are exact duplicates of each other, but which are so constructed that they can be arranged in alternate position in a device to build up a composite heating unit of any optional number of individual parts all of which can be machine made for uniformity and safety and assembled on a production schedule.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claim, any modified forms of structure or use of miechanical equivalents, which may be reasonably included within its scope.

I claim as my invention:

A heating unit for an electric appliance comprising a frame, a length of resistance wire and a plurality of identical sheets of homogeneous heat resistant insulating material positioned vertically and separated from one another in the frame and apertured at the edges for spacing thereon turns of a coil of said wire wound in the same relation with turns at intervals closer together at the bottom than at the top for more even heat distribution, and provided at one end with a system of holes separated from the outermost turn of said coil, said sheets being adapted to be individually mbchine wound with the wire so that the ends terminate at opposite sides and ends of the. sheets and adapted to be secured to the frame with each adjacent sheet reversed side for side to position alternate ends of the coil adjacent each other in the same relative position, said coil ends having welded joints connecting them together when in place thereby to preserve identical windings on each sheet, said system of holes being adapted to accommodate one free end of the composite coil so formed for threading it back along one end of the alternate sheets in insulated position from the turns of the coil to a point adjacent the other free end of said coil.

I HARRY COLLINS. 

